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Rule for initial TCP SYN packet
From: Thomas Hyslip <thomas.hyslip () gmail com>
Date: Thu, 9 Jan 2014 10:51:15 -0500


I'm trying to write a rule to catch the first TCP packet for new sessions
that have the SYN flag set.  But, I'm not seeing anything.  If I remove the
flag:S option i see everything, any suggestions? here is the rule I have
set now.  If I craft a packet with hping3, Snort alerts, but I thought this
would catch all new TCP connections to webpages.

alert tcp $HOME_NET any -> any 80 (msg:"egress filter tcp traffic to port
80 with syn flag set"; flow: stateless; flags:S; classtype:test;
sid:1000001; rev:1;)

BTW, this is not for production, just doing some research on a topic.

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